Method of coating a tampon with an insertion aid

ABSTRACT

A method for applying a normally solid lubricant to the tip of a precompressed tampon. The solid lubricant is first melted to a fluid state, then formed into a bead. A portion of the bead surface is congealed and the bead then molded around the tampon tip and solidified.

United States Patent [191 Suchane METHOD OF COATING A TAMPON WITH ANINSERTION AID [75] lnventor: David V. Suchane, Menasha, Wis.

[73] Assignee: Kimberly-Clark Corporation,

Neenah, Wis.

[22 Filed: Nov. 17, i972 [21] Appl. No.: 307,588

Related US. Application Data [62] Division of Ser. No. 165,134, July22,1971, Pat. No.

[52] US. Cl 264/257, 264/259 [51] lnt. Cl 82% 9/02 [58] Field of Search264/257, 259,324, 271

[56] References Cited UNITED STATES PATENTS 2,639,252 5/1953 Simon et al264/257 [451 June 28, 1974 3,184,527 5/1965 Fischer 264/257 11/1966Clark .L ..264/267 Primary Examiner-Robert F. White AssistantExaminer-T. E. Balhoff Attorney, Agent, or Firm-Daniel .1. Hanlon, .lr.;William D. Herrick; Raymond J. Miller [57 ABSTRACT A method for applyinga normally solid lubricant to the tip of a precompressed tampon. Thesolid lubricant is first melted to a fluid state, then formed into abead. A portion of the bead surface is'congealed and the head thenmolded around the tampon tip and solidified.

7 Claims, 4 Drawing Figures PATENTED JUN 2 8 I974 I ll/47111111 METHODOF COATING A TAMPON WITH AN INSERTION AID This is a division of copeningU.S. Pat. application Ser. No. 165,134, filed July 22, 1971 now U.S.Pat. No. 3,724,465 on Apr. 3, 1973.'

BACKGROUND OF THE INVENTION In the manufacture of compressed absorbenttampons, and especially those of the type which are inserted into bodycavities without the aid of an insertion tube or a lubricous cover andthus present an inherently dry surface to the body, it is desirable tocoat at 7 least the leading end or tip of the tampon with an inserart isreplete with proposed solutions to this problem.

While some aspects are successfully solved by the various proposals,others seem to appear with vexing regularity. It is well known, forexample, as described in assignees U.S. Pat. No. 3,428,044 of Feb. 18,1969; that normally solid polyethylene glycols of an average molecularweight of about 1,000 and above, when coated on the tip of aprecompressed tampon will provide a surface lubricity suitable for useas an insertion aid. However, it was found that at the elevatedtemperatures which frequently occur inwarehousing and ship ping, thistype of coating softens enough to permit migration of the coating intothe body of the tampon. Under such conditions the surface where thecoating had been applied then eventually reverts in appearance and feelto that of an uncoated tampon. Asa result the desired lubricity is lost.In assignees U.S. Pat. application Ser. Nol 807,490 filed Mar. 17, 1969and now U.S. Pat. No. 3,595,236 a more stable polyethylene glycolcoating is described in which the stability and opacity of mixtures ofspecified molecular weight polyethylene glycols are .improved by theaddition of starch. While this composition was found to be animprovement over' earlier type Coatings, it, stilllacked the desiredlong term stability. This invention is directed to a polyethylene glycolcoating formulation which overcomes most of the disadvantages formerlyencountered. A preferred method of applying the coating to a tampon tipis also disclosed. Accordingly, an important object of the presentinvention is to provide an improved insertion-aid coating forprecompressed tampons which coating remains stable during long termshipment and storage.

Another object is to provide a suitable method for applying the improvedcoating and similar coating materials fo precompressed tampons.

SUMMARY OF INVENTION 2 tip of a precompressed tampon which is to becoated. The die is maintained at a temperature less than the meltingpoint of the mixture. When the mixture is' injected into the cooled diecavity it forms a head which becomes partially congealed on its outersurface due to contact with the cooled cavity, but the major portion ofthe interior remains fluid and mobile. The tip of the precompressedtampon is pressed into the cavity containing the internally mobilemixture wherebythe mixture is molded around-the tampon tip to form asmooth cast coating. When the tampon is withdrawn, the molded coatingreadily releasesfrom the cavity without leaving residue. Apparently thisis due to the lubricating properties of the adjuvant as well as theslight shrinkage of the coating as it hardens. The tampon tip is thusprovided with a smoothly molded coating. The tampon may also be axiallyrotated in the die during the molding operation. This axial rotationstep speedsup the setting or hardening of the coating, which isdesirable when using lower molecular weight polymers. It also results ina dull, matte surface rather than the smooth cast surfacenoted above.

In addition to facilitating residue-free release from the cavity thedispersed adjuvant has other functions which improve performance andappearance of the finished tampons. One is that it stabilizesthe-polyethylene glycol coating so that the coating remains in freshcondition and does not migrate into the tampon or leave a dry surfaceeven after a prolonged exposure at temperatures of F. Another is that itprovides an opaque color and cosmetic appearance to the coated surface.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings: i

FIG. 1 is a schematic illustration of a means suitable for carrying outthe method for coating tampons in accordance with this invention;

FIG. 2 is a section of a die cavity taken at 22 of FIG. 1 showing ametered amount of lubricant mixture disposed therein.

DESCRIPTION OF. THE PREFERRED EMBODIMENTS As indicated above, thisinvention is particularly directed to an improved insertion-aid coatingfor precompressed self-sustaining tampons and a method for applying thecoatingwhile in a mobile condition to the tip portion of the tampon. Theprimary coating material is a normally solid polyethylene glycol and theimprovement comprises the addition of particular stabilizing agents tothe polyethylene glycol.

As shown in FIG. 4 of the drawings, the preferred tampon 30 comprises abody of absorbent material 4 compressed to a self-sustaining cylindricalshape with a substantially hermispheric frontal portion or tip, and

having a withdrawal string 31 attached to the rear portion. The tamponmay be adapted for use for stick insertion by having an axiallyextending socket 32 centrally drilled part way into the rear portioninto which a removable stick 33 may beseated. For digital insertion, thesocket is not required.

FIG. 1 illustrates one method for carrying out the invention. Thenumeral 11 generally indicates a melting, mixing and injecting devicefor the polyethylene glycol. The device as shown comprises a heated tank112 into which a normally solid polyethylene glycol is melted to a fluidstate as indicated at 13. A small amount of a finely-powderedwater-insoluble adjuvant selected from the group consisting of metalstearates and/or fumed silica is introduced into tank 12 through port 14and dispersed in the melted polyethylene glycol by mixing device 15driven by motor 16. Preferably the mixer is run continuously to providea uniform dispersion. Connected to tank 12 is an extruder or ejectormeans 18 which is also equipped with a metering device I7 for meteringthe amount of the fluid polyethylene glycol mixture it is desired toeject.

A rotatable turntable 19 is disposed beneath ejector 18. The upper faceof turntable 19 is provided with series of die cavities 20 disposedadjacent the circumference. Each die cavity 20 has an interiorconfiguration which substantially conforms to the shape of the tampon itis desired to coat. The cavity shown is hemispheric and conforms to therounded tampon tip shown in the drawings. The interior of turntable 20is hollow and is preferably filled with 'a circulating coolant fluid 21(FIGS. 2 and 3) which surrounds the outer wall of cavities 20 dependingfrom the top wall of turntable I9 to maintain the dies 20 at atemperatue below the melting point of the polyethylene glycol mixture.The coolant is fed through axially disposed tube 22 and removed at 23through a concentric channel as indicated.

In operation, a metered amount 24 of the melted polyethylene glycolmixture containing the specified adjuvant is injected in timed sequenceinto each of the cavities 20 on turntable 19 as each cavity is rotatedunderneath ejector means 18. The turntable 19 may, of course, be rotatedcontinuously or intermittently as desired.

The ejected fluid 24 forms a bead 25 in the bottom of the cavity asshown in FIG. 2. It will be seen that in this condition only a smallportion of the bead surface is in contact with the cooled surface of thedie cavity, so that only a small surface area of the bead 25 willcongeal or start to solidify while the major portion remains mobile.After each cavity receives an injection of the coating mixture, theturntable continues to rotate past the ejection device, and the tip of atampon 20 is pressed into the mixture-containing cavity at station B. Asthe tampon tip is pressed into the cavity it causes the polyethyleneglycol mixture to flow and mold itself around the tampon tip in the formof a thin cast coating as shown at 34 in FIGS. 3 and 4. As the turntable19 continues to rotate the cooling liquid 21 surrounding the die cavityreduces the temperature of the molded polyethylene glycol mixture belowits melting point, causing the mixture to rapidly congeal and hardeninto a solidified condition. The coated tampon with a' molded cap 34 ofthe polymer mixture on the tip thereof, as shown in FIG. 4, is thenremoved at station C. If desired the tampon may also be rotated axiallyon itslf as turntable moves the tampon from station B to station C. Thisaxial rotation step speeds up the hardening of the coating, but resultsin a dull, matte finish.

In the above-described process, it was found that the use of thespecified adjuvant permits easy removal of the coated tampon from thedie, leaving no residue. This easy release may be attributed to theadditional lubricating ability contributed by the adjuvant, but may alsocome from the fact that the polyethylene glycol takes a firmer set withthe adjuvant mixed therein.

The following Examples will set forth several specific embodiments ofthe invention.

Tampons with hemispherical tips as shown in the drawings were coated inthe manner described with each of the formulations described below. Inthese formulas, polyethylene glycol with an average molecular weight of1,000 is identified as PEG 1,000 and polyethylene glycol with an averagemolecular weight of4,000 is identified as PEG 4,000. All parts are partsby weight. In each instance, the PEG 1,000 was heated to about 158 F toreduce it to a fluid state. The die cavity was maintained at about roomtemperature.

Example A. PEG 1,000 alone. Example B. Ten parts PEG 1,000, one part10a. Example C. Ten parts PEG 1,000, one part fumed silica, one partmagnesium stearate. Example D. Ten parts PEG 1,000, one part fumedsilica, one part aluminum stearate. Example E. Ten parts PEG 1,000, onepart fumed silica, one part zinc stearate. Example F. Ten parts PEG1,000, one part fumed silica, one part calcium stearate. Example G. Tenparts PEG 1,000, one part magnesium stearate. Example H. Ten parts PEG1,000, one part alumifumed silnum stearate. Example I. Ten parts PEG1,000, one part zinc stearate. 1 Example 1. Ten parts PEG 1,000, onepart calcium stearate.

After tampons were coated with each of these mixtures, they were placedin a forced air oven at F. for 16 hours. At the end of that time, theExample A coating consisting of PEG 1,000 alone had completely migratedinto the tampon. The coating formulations consisting of PEG 1,000 andfumed silica Example B) as well as those containing PEG 1,000, fumedsilica and a metal stearate (Examples C, D, E, F) all remained on thesurface of the tampons andretained essentially all of their originalsmoothnessand lubricity. Those formulations containing PEG 1,000 and ametal stearate (Examples G, H, I, .I) remained on the surface ofthetampon but appeared to lose some lubricity. However, this loss wasnot enough to make the coating defective.

The coatings containing PEG 1,000 and the zinc stearate, the magnesiumstearate, and the calcium stearate were a little drier and stickier thansimilar coatings which also contained fumed silica, while the coatingcontaining PEG 1,000 and aluminum stearate took on a somewhat mottledappearance which was absent in the same coating containing fumed silica.In each case, however, the desired stability was present.

It will be noted therefore that while the metal stearate may be usedalone, the combination of stearates with fumed silica is superior.

The above experiments were repeated except that in each of theformulations PEG 4,000 was used instead of PEG 1 .000. Each of thecoated tampons were heated for 16 hours at 150 F to test stability. Theresults were substantially the same as those obtained when PEG 1,000 wasused in the formulas.

In each case the metal stearate and fumed silica is added to the coatingby simply blending it into the hot PEG melt. The fumed silica has beenfound to exert a thixotropic effect upon the formulation. That is, theformulation containing fumed silica remains very fluid while it is beingstirred but when stirring stops, the formulation begins to thicken,eventually reaching a marshmallow type consistency. Upon stirring, thestructure is rapidly broken down and the formulation becomes very fluidonce more.

This thixotropic effect has been found to be advantageous for tamponcoatings. The tampon is coated with the formulation in the hot fluidstate so that the mixture readily flows around the tip as it is pressedinto the die. However, because it is thixotropic when containing fumedsilica, the coating does not become fluid when similar temperatures arereached during storage of the coated tampon due to the absence ofphysical agitation. It is believed this phenomenon also aids inpreventing migration of the coating into the body of the tampon.

Fumed silica is silicon dioxide formed by the vapor phase hydrolysis ofsilicon tetrachloride. It is supplied as a low density water-insolublepowder with extremely small particle size and a large surface area.Although it is insoluble, the powder forms a clear, colloidal suspensionin water. The grade of fumed silica used in the Examples described issoldunder the trademark CAB-O- SlL by Cabot Corporation. It has beenapproved by the FDA for use in foods and pharmaceuticals.

The metal stearates may be used in their conventional commercial formwhich are water-insoluble pow: ders. FDA approved grades should ofcourse be used.

As indicated above, the polyethylene glycol should be one that isnormally solid at room temperature. While PEG 600 has a melting pointrange of about 68 to 77 F and can meet the definition, it is marginal inperformance, and it is preferred that polyethylene glycols with anaverage molecular weight of about 1,000 and above be used. The preferredrange is from about 1,000 to about 6,000. Lower molecular weightpolymers may of course be used in admixture with higher weight polymersto obtain average molecular weights in the preferred range. Methoxypolyethylene glycol with an average molecular weight of about 750 mayalso be used.

While the description of the specific examples have been confined topolyethylene glycol and adjuvant mixtures, it will readily be seen thatthe method of-application itself can readily be used for other coatingswhich are solid at room temperature but fluid at elevated temperature.

The described method has been found to be superior to the older methodsof dipping the compressed tampon tip into the molten polyethylene glycolor of spraying partially congealed material onto the tip. By thedescribed method much better control over the thickness and uniformityof the applied coating is possible. In addition, less coating materialis required, providing advantages in both economy and performance.

absorbent tampon with an insertion-aiding lubricant,

said method comprising the steps of melting a normally solid lubricantto a fluid state, dispensing a small predetermined quantity of saidlubricant in the form of a bead while said lubricant is in said fluidstate, cooling said bead to partially congeal at least a portion of thesurface of said bead such that said congealed bead will not migrate intothe tip of said tampon, molding said partially congealed bead aroundthe-tip of said co'mpressed tampon while completely congealing saidlubricant to a solid state by continuing to cool said lubricant to atemperature below its melting point.

2. A method for coating the rounded tip of a precompressed tampon withan insertion-aiding lubricant mixture, said method comprising the stepsof melting a nor mally solid lubricant to a fluid state, dispersing insaid melted lubricant a finely-powdered, water-insoluble adjuvant,providing a die cavity having-an internal configuration which conformsto the shape of said tampon tip, injecting a small metered amount ofsaid fluid mixture into said die cavity while said die is maintained ata temperature less than the melting point of said lubricant mixturewhereupon at least the outer portion of said mixture in contact withsaid die begins to set, pressing the tip of said precompressed tamponinto said cavity and into contact with said partially set lubricantmixture while the interior of said lubricant mixture is still mobile toform and to set said lubricant mixture around said tip without migrationtherein while main taining said temperature at less than said meltingpoint, and withdrawing the tampon from said cavity whereby the tip ofsaid tampon is provided with a smooth cast coating of said lubricantmixture.

3. The method of claim 2 wherein said normally solid lubricant is apolyethylene glycol.

.4. The method of claim 2 wherein said normally solid lubricant is apolyethylene glycol with an average molecular weight in the range ofabout 1,000 and about 6,000.

5. The method of claim 2 wherein said normally solid lubricant is amethoxy polyethylene glycol with an average molecular weight of about750.

6. The method of claim 2 wherein said adjuvant is selected from thegroup consisting of metal stearates and fumed silica.

7. The method of claim 6 wherein said metal stearate is selected fromthe group consisting of aluminum, calcium, magnesium and zinc stearate.

ro-j UNITED STATES PATENT OFFICE x CERTIFICATE OF CORRECTION PatentNo.3,821,350 Dated June 974 Iuvenwfls) David V. Duchane It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Inventor "David V. Suchane" should read David V. Duchane Column 1, line56, "0" should read to Column 4, line 40, after "silica" ,and before"Example" insert a parentheses,- 1

Signed and sealed this 8th day of October 1974.

(SEAL) I Attest:

McCOY M. GIBSON JR. I C. MARSHALL DANN Attesting Officer Commissioner ofPatents

2. A method for coating the rounded tip of a precompressed tampon withan insertion-aiding lubricant mixture, said method comprising the stepsof melting a normally solid lubricant to a fluid state, dispersing insaid melted lubricant a finely-powdered, water-insoluble adjuvant,providing a die cavity having an internal configuration which conformsto the shape of said tampon tip, injecting a small metered amount ofsaid fluid mixture into said die cavity while said die is maintained ata temperature less than the melting point of said lubricant mixturewhereupon at least the outer portion of said mixture in contact withsaid die begins to set, pressing the tip of said precompressed tamponinto said cavity and into contact with said partially set lubricantmixture while the interior of said lubricant mixture is still mobile toform and to set said lubricant mixture around said tip without migrationtherein while maintaining said temperature at less than said meltingpoint, and withdrawing the tampon from said cavity whereby the tip ofsaid tampon is provided with a smooth cast coating of said lubricantmixture.
 3. The method of claim 2 wherein said normally solid lubricantis a polyethylene glycol.
 4. The method of claim 2 wherein said normallysolid lubricant is a polyethylene glycol with an average molecularweight in the range of about 1,000 and about 6,000.
 5. The method ofclaim 2 wherein said normally solid lubricant is a methoxy polyethyleneglycol with an average molecular weight of about
 750. 6. The method ofclaim 2 wherein said adjuvant is selected from the group consisting ofmetal stearates and fumed silica.
 7. The method of claim 6 wherein saidmetal stearate is selected from the group consisting of aluminum,calcium, magnesium and zinc stearate.